Cooling system with desiccant dehumidification

ABSTRACT

A system for removing heat from electrical systems includes a dehumidification device including a desiccant, an evaporative cooling device, air moving devices, and an air flow control devices. The air moving device moves air through the dehumidification device, the evaporative cooling device, and the electrical systems. The air flow control device controls a rate of flow through the dehumidification device.

BACKGROUND

Electronic components generate waste heat energy when in use. This heatenergy should be removed to mitigate a potential for componentoverheating and subsequent malfunction. Computer systems typicallyinclude a number of such components, or waste heat sources, thatinclude, but are not limited to, printed circuit boards, mass storagedevices, power supplies, and processors. For example, one personalcomputer system may generate 100 watts to 150 watts of waste heat andsome larger computers with multiple processors may generate 250 watts ofwaste heat. Some known computer systems include a plurality of suchlarger, multiple-processor computers that are configured intorack-mounted components, and then are subsequently positioned within aracking system. Some known racking systems include 40 such rack-mountedcomponents and such racking systems will therefore generate as much as10 kilowatts of waste heat. Moreover, some known data centers include aplurality of such racking systems.

Some known data centers include methods and apparatus configured tofacilitate waste heat removal from a plurality of racking systems.Moreover, some known data centers include a plurality of racking systemsthat have a plurality of configurations that are non-uniform withrespect to component density and usage such that each racking systemgenerates waste heat at a non-uniform rate as compared to the remainderof the racking systems. In such data centers, application of uniformheat removal methods and apparatus to such non-uniform waste heatgeneration sources may not be fully efficient and effective in wasteheat removal.

Some data centers use outside air as an important source of cooling air.The characteristics and quality of outside air may vary widely, however,even at a given location. Aside from the significant changes intemperature and humidity that can occur with the change of seasons,environmental quality of the outside air may vary due to a myriad ofexternal factors. These variations over time in availability, coolingcapacity, and quality of outside air create challenges in effectivelysizing and operating cooling air systems for a data center. For example,a mechanical cooling system that is sized for cooler, drier times ofyear may fail to provide adequate cooling in hot, humid weather.Conversely, a mechanical cooling system that is sized to provideeffective cooling during hot, humid summer months may result in a systemthat is significantly oversized for cooler, drier times of year.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a data center including a venturisection in which a two-phase mixture of air and water droplets can beformed.

FIG. 2 illustrates one embodiment of a data center including a venturisection and a bypass duct for mixing a two-phase mixture of air and mistwith return air.

FIG. 3 illustrates one embodiment of a data center including a venturisection and a desiccant wheel that can be operated to dry out atwo-phase mixture of air and water droplets.

FIG. 4 illustrates one embodiment of a desiccant wheel.

FIG. 5 illustrates one embodiment of data center with a desiccant wheelwith dampers to control air flow to the desiccant wheel, and a desiccantbypass duct.

FIG. 6 illustrates one embodiment of data center with multiple desiccantwheels with dampers to control air flow to the desiccant wheels.

FIG. 7 illustrates a data center with a heat exchanger for transferringheat from electrical loads in the data center to a desiccantreactivation loop.

FIG. 8 illustrates a data center with a solar heating system to promotedesiccant reactivation.

FIG. 9 illustrates one embodiment of a building with a desiccant wheelwith a counter-flow arrangement for desiccant reactivation.

FIG. 10 illustrates one embodiment of cooling electrical systems in adata center using a two-phase mixture of air and water droplets.

FIG. 11 illustrates one embodiment of cooling electrical systems in adata center with controlled flow of air to a desiccant wheel.

FIG. 12 is a fluid schematic diagram illustrating one embodiment of anevaporative cooling system including upper and lower evaporative mediabanks.

The various embodiments described herein are susceptible to variousmodifications and alternative forms. Specific embodiments are shown byway of example in the drawings and will herein be described in detail.It should be understood, however, that the drawings and detaileddescription thereto are not intended to limit the disclosure to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents and alternatives falling within thespirit and scope of the appended claims. The headings used herein arefor organizational purposes only and are not meant to be used to limitthe scope of the description or the claims. As used throughout thisapplication, the word “may” is used in a permissive sense (i.e., meaninghaving the potential to), rather than the mandatory sense (i.e., meaningmust). Similarly, the words “include,” “including,” and “includes” meanincluding, but not limited to.

DETAILED DESCRIPTION OF EMBODIMENTS

Various embodiments of a system and method for cooling electronicequipment in a data center are disclosed. According to one embodiment, asystem for cooling heat producing components in a building includes aduct coupled to a room of the building and one or more air movingdevices. The duct includes a venturi section. The air moving devicesmove air through the venturi section of the duct such that at least aportion of water in the air is converted from water vapor to waterdroplets. The water droplets are carried downstream from the venturisection in a two-phase mixture including air and water.

According to one embodiment, a system for cooling heat producingcomponents in a building includes a duct coupled to a room of thebuilding and one or more air moving devices. The duct includes aconstricted section. The air moving devices move air through theconstricted section of the duct such that water in the air is convertedfrom water vapor to water droplets. The water droplets are carrieddownstream from the constricted section in a two-phase mixturecomprising air and water.

According to one embodiment, a method of removing heat from electricalsystems in a building includes moving air through a constricted sectionof a duct such that at least a portion of water in the air is convertedfrom water vapor to water droplets. A two-phase mixture air and thewater droplets is moved. Electrical devices are cooled using thetwo-phase mixture.

According to one embodiment, a data center includes electrical devicesand a cooling system. The cooling system includes a desiccant wheel, anevaporative cooling device downstream from the desiccant wheel, an airmoving device, and an air flow control device. The air moving devicesmoves air through the desiccant wheel, the evaporative cooling device,and across heat producing components of the electrical devices. The airflow control device controls the flow of through at least one of thedesiccant wheels.

According to one embodiment, a system for removing heat from electricalsystems includes a dehumidification device including a desiccant, anevaporative cooling device, and air moving devices, and an air flowcontrol devices. The air moving device moves air through thedehumidification device, the evaporative cooling device, and theelectrical systems. The air flow control device controls a rate of flowof through the dehumidification device.

According to one embodiment, a method of removing heat from electricalsystems includes controlling a rate of a flow of one or more streams ofair. A stream of air is passed across a desiccant to remove water vaporfrom the air. The stream of air is moved through a wetted media. Heat isremoved from electrical systems using the air from the wetted media.

As used herein, “data center” includes any facility or portion of afacility in which computer operations are carried out. A data center mayinclude servers and other systems and components dedicated to specificfunctions (e.g., e-commerce transactions, database management) orserving multiple functions. Examples of computer operations includeinformation processing, communications, simulations, and operationalcontrol.

As used herein, “mechanical cooling” means cooling of air by a processthat involves doing mechanical work on at least one fluid, such asoccurs in vapor-compression refrigeration systems.

As used herein, “evaporative cooling” means cooling of air byevaporation of liquid.

As used herein, “direct evaporative cooling” means cooling of air byevaporation of liquid directly into a stream of air to be cooled.

As used herein, “adiabatic system” means a system that cools byevaporation of a liquid.

As used herein, “ambient” refers to a condition of outside air at thelocation of a system or data center. An ambient temperature may betaken, for example, at or near an intake hood of an air handling system.

As used herein, “computing device” includes any of various devices inwhich computing operations can be carried out, such as computer systemsor components thereof. One example of a computing device is arack-mounted server. As used herein, the term computing device is notlimited to just those integrated circuits referred to in the art as acomputer, but broadly refers to a processor, a server, amicrocontroller, a microcomputer, a programmable logic controller (PLC),an application specific integrated circuit, and other programmablecircuits, and these terms are used interchangeably herein. Some examplesof computing devices include e-commerce servers, network devices,telecommunications equipment, medical equipment, electrical powermanagement and control devices, and professional audio equipment(digital, analog, or combinations thereof). In various embodiments,memory may include, but is not limited to, a computer-readable medium,such as a random access memory (RAM). Alternatively, a compact disc-readonly memory (CD-ROM), a magneto-optical disk (MOD), and/or a digitalversatile disc (DVD) may also be used. Also, additional input channelsmay include computer peripherals associated with an operator interfacesuch as a mouse and a keyboard. Alternatively, other computerperipherals may also be used that may include, for example, a scanner.Furthermore, in the some embodiments, additional output channels mayinclude an operator interface monitor and/or a printer.

As used herein, a “damper” includes any device or component that can bemoved to control (e.g., increase or decrease) the flow of fluid througha duct or other passageway. Examples of dampers include plates, blades,panels, or discs, or any combination thereof. A damper may includemultiple elements. For example, a damper may include a series of platesin parallel relation to one another that can be simultaneously rotatedto close a duct. As used herein, to “position” a damper means to placeor leave one or more elements of the damper to achieve desired flowcharacteristics through the damper, such as open, closed, or partiallyopen. In a system with four air handling sub-systems, positioning theoutside air dampers may include opening outside air dampers in one ofthe sub-systems and keeping outside air dampers closed in the otherthree sub-systems.

As used herein, a “free cooling mode” includes a mode of operation inwhich an air handling sub-system pulls air at least partially from anexternal source (such as air outside a facility) and forces the air toelectronic equipment without active chilling in the air-handlingsub-system (e.g., fluid flow through the chiller coils in the airhandling sub-system is shut off by closing a flow control valve).

As used herein, “room” means a room or a space of a building. A“computer room” means a room in which computer systems, such asrack-mounted servers, are operated.

In some embodiments, a cooling system includes a dehumidificationsystem. In certain embodiments, the dehumidification system is locatedupstream from other apparatus in the cooling system, such as anevaporative cooling system. A dehumidification system may provide air toa data room and/or cooling apparatus in an air handling sub-system thatis relatively dry as compared, for example, to outside air.

In some embodiments, a system with a duct with constricted section inwhich water vapor is converted into water droplets. The water dropletsare carried downstream in a two-phase mixture of air and water. At leasta portion of the water droplets are removed from the mixture.

In some embodiments, a system for cooling heat producing components in abuilding includes a duct with a venturi section in which water vapor inthe air is converted into water droplets (for example, mist). The waterdroplets are carried downstream from the venturi section in a two-phasemixture of air and water. The water droplets may be removed from themixture.

FIG. 1 is a schematic view of an embodiment of a data center coolingsystem including a dehumidification system and a direct evaporativecooling section. Cooling system 100 may remove heat from computersystems operating in data center 102. In the embodiment illustrated inFIG. 1, cooling system 100 includes air handling sub-system 104. Airhandling sub-system 104 may channel cooling air to data center 102.

The number of air handling sub-systems 104 in cooling system 100 mayvary. In some embodiments, cooling system 100 includes many air handlingsub-systems 104. In one embodiment, cooling system 100 may include fourair handling sub-systems 104. In another embodiment, cooling system 100includes only one air handling sub-system 104. In facilities withmultiple air handling sub-systems and/or multiple data centers,cross-over ducts may be provided (e.g., on the supply side, the returnside, or both) to allow cooling air from air handling sub-systems to bedistributed and/or redirected within a data center or among datacenters. Air handling sub-systems may be commonly controlled, separatelycontrolled, or a combination thereof. In certain embodiments, only asub-set of the total air handling sub-systems for a data center areprovided with outside air vents. For example, half the air handlingsystems at a data center may have both outside air vents and return airvents, while the other half the air handling systems at a data centerhave only return air vents.

Each air handling sub-system 104 may be coupled to data center 102 bysupply duct 108 and return duct 110. Cooling air may flow from airhandling sub-system 104 through supply duct 108 into plenum 112. Fromplenum 112, cooling air may pass through flow restriction devices 114into room 116. Cooling air may pass over racks 118. After the air isheated by racks 118, the air may pass through return duct 110. Air maybe recirculated through one or more air handling sub-systems ordischarged from the system through exhaust vent 120. Exhaust vent 120includes exhaust damper 122.

Air for cooling system 100 may be drawn from outside air, recirculatedair, or a combination of outside air and recirculated air. Air handlingsub-system 104 includes outside air vent 124. Outside air vent 124includes outside air damper 126. Air handling sub-system 104 includesmixing air damper 130.

Cooling system 100 includes dehumidification system 132, evaporativecooler 136, supply fan 138, and return fan 144. Cooling system 100includes bypass duct 140. Bypass duct 140 may allow for all or a portionof the supply air to bypass evaporative cooler 136. Evaporative coolerbypass damper 141 and evaporative cooler face damper 142 may beselectively positioned to control flow through evaporative cooler 136.Cooling system 100 includes return air bypass 151 and return air bypassdamper 152. Supply fan 138 and return fan 144 are coupled to VFDs 146.VFD 146 is coupled to control unit 150.

Dehumidification system 132 includes duct 170, impingement plate system172, and bypass system 173. Duct 170 includes venturi section 174.Venturi section may be in the form a venturi nozzle. Venturi section 174includes a constricted section in which the cross-sectional area of theduct is reduced. Venturi section 174 includes converging section 176,reduced section 178, and diverging section 180. Venturi section 174 maybe a two-dimensional venturi shape or a three-dimensional venturi shape.

Outside air, return air, or a combination of both may be provided assource air. Source air may be drawn through venturi section 174 bysupply fan 138. At reduced section 178, air velocity is increased andpressure is decreased relative to the velocity and pressure of the aircoming into venturi section 174. At or near reduced section 178, aportion of the water vapor in the air may come out of saturation, suchthat water droplets are formed in the air. A multi-phase mixture of airand mist may be formed. In certain embodiments, the temperature atreduced section 178 may drop.

Impingement plate system 172 includes plates 182, drain pan 184 anddrainpipe 186. Supply fan 138 draws air from venturi section 174 andacross impingement plate system 172. Impingement plate system 172 mayserve as a water removal device. As a mixture of air and water dropletsfrom venturi section 174 flows across plates 182, water may accumulateon plates 182 (for example, in the form of condensate). Water on platesmay drop from plates 182 and collect in drain pan 184. Water collectedin drain pan 184 may be carried away from air handling sub-system 104 indrainpipe 186.

Supply fan 138 moves air that has passed through condensate plate system172 through evaporative cooler 136. Because some of the water in thesource air has been removed, the air supplied to evaporative cooler 136may be relatively dry. Providing relatively dry air to evaporativecooler 136 may increase effectiveness of the cooling system.

Bypass system 173 includes a duct and a set of dampers that allows airto bypass either or both of venturi section 174 and impingement platesystem 172.

In FIG. 1, impingement plate system 172 is shown, for illustrativepurposes, as downstream from constricted section 178. A water removaldevice may nevertheless, in some embodiments, be located at a differentlocation relative to the constricted section of a duct. For example, animpingement plate for collecting water may be located at the narrowestsection of a duct (for example, reduced section 178) or in a divergingportion of a duct (for example, diverging section 180). In someembodiments, a water removal device is positioned in a duct to optimizeremoval of mist from a two-phase mixture of air and mist.

In cooling system 100 illustrated in FIG. 1, dehumidification system 132can be used to dehumidify air from outside air, recirculated air, or acombination of outside air and recirculated air, depending on the modeof operation of cooling system 100.

Control unit 150 may be programmed to control devices in air handlingsub-systems 102 and dehumidification system 132. Control unit 150 iscoupled to supply fan 138, return fan 144, outside air damper 126,exhaust damper 122, and mixing air damper 130. Control unit 150 is indata communication with temperature sensors, humidity sensors, andpressures sensors. For example, control unit 150 is in datacommunication with temperature sensor 190 located near the intake hoodof cooling system 100. In one embodiment, control unit 150 is in datacommunication with sensors 192 at a location downstream fromdehumidification system 132.

In one embodiment, all of the air handling sub-systems anddehumidification systems at a data center are controlled with a commoncontrol unit. In other embodiments, separate controllers are providedfor each air handling sub-system and dehumidification sub-system, or fora subset of the air handling sub-systems and/or dehumidificationsub-systems. Devices in air handling sub-systems and dehumidificationsub-systems may be controlled automatically, manually, or a combinationthereof.

In certain embodiments, control unit 150 includes at least oneprogrammable logic controller. The PLC may, among other things, open andclose dampers in air handling system 104 based upon command signals froman operator to channel air flow through data center 102 as necessary forthe prevailing operational conditions. Alternatively, the PLC maymodulate dampers between fully open and fully closed positions tomodulate airflow.

Cooling system 100 also includes a plurality of temperature measurementdevices that, in one embodiment, are thermocouples. Alternatively, thetemperature measurement devices include, but not be limited to,resistance temperature detectors (RTDs) and any device that facilitateoperation of cooling system 100 as described herein.

In the embodiment shown in FIG. 1, air handling sub-system 104 may forceair through supply duct 108 into plenum 112. In other embodiments,cooling air may be forced directly into room 116 through a supply ductwithout going through a plenum. In various embodiments, flow restrictiondevices 114 may be chosen to control the flow rates and distribution ofcooling air among various racks 118 in room 116.

In various embodiments, operation of one or more air handlingsub-systems, dehumidification systems, or evaporative cooling devices ofa cooling system may be controlled in response to one or moreconditions. For example, the controller may be programmed to switch theair source for an air-handling sub-system from return air to outside airwhen one or more predetermined conditions are met, such as temperatureand humidity.

In various embodiments, a cooling system for a data center may beoperated in two or more different modes. The mode of operation at anygiven time may be selected based on characteristics of the outside air,characteristics of air in various locations in the cooling system, andother characteristics prevailing at or near the data center. In variousembodiments, the multi-mode cooling system may minimize the amount ofenergy required to cool a data center. The multi-mode system may allowfor a more efficient use of components of a cooling air system, allowfor a reduction is size/capacity of one or more elements of the system,reduce operating costs of a cooling system, and/or improve coolingeffectiveness (such as through lower operating temperatures of computersystems in the data center).

In some embodiments, cooling of a data center includespre-dehumidification of source air (such as outside air). In oneembodiment, the outside air temperature and/or temperature upstream fromthe dehumidification system is monitored and the fluid in thedehumidification coils is maintained a few degrees cooler than themeasured air temperature. The outside air may be relatively hot andhumid air, such may be found in southern Florida during summer months.Air exiting the dehumidification system may be relatively hot and dry.In one embodiment, the mode of cooling may be evaporative cooling. Insome embodiments, the mode of cooling may be a hybrid mode that includesmechanical cooling and evaporative cooling. In certain embodiments, theoperating parameters of the dehumidification system are controlled toachieve desired characteristics in the supply air to the coolingapparatus. In one embodiment, water in the coils of the dehumidificationsystem is maintained at a temperature that is a few degrees cooler thanthe outside air and/or incoming air into the dehumidification system. Incertain embodiments, air from the data room may be recirculated througha dehumidification system and/or cooling apparatus.

The sequence in which control conditions are assessed may differ fromembodiment to embodiment. Control conditions may be monitored over time(continuously or at regular or irregular intervals), and mode switchingaccomplished based on changes in the conditions. A dehumidificationsystem may be active or inactive in the various modes of operationdescribed herein, either continuous or based on air conditions.

In one embodiment, supply fans in a building are 180,000 cubic feet perminute, QEP-54 manufactured by Greenheck. In one embodiment, return fansin a building are 180,000 cubic feet per minute, ATLI 0-40T2manufactured by Comefri.

In some embodiments, a multi-phase mixture of air and liquid water (forexample, mist) is mixed with return air from heat producing componentsin a building. FIG. 2 illustrates one embodiment of a data centerincluding a venturi section and a bypass duct for mixing a two-phasemixture of air and mist with return air. The system shown in FIG. 2 maybe similar to that described above relative to FIG. 1. Cooling system200 includes venturi section 174, mixing region 202, and bypass 204.Mixing region 202 may be selectively placed in fluid communication withreturn duct 110 by way of vent 206. Dampers 208 may be operated tocontrol the flow of air from return duct 110 to mixing region 202.

Source air may be drawn through venturi section 174 by supply fan 138.At reduced section 178, air velocity is increased and pressure isdecreased relative to the velocity and pressure of the air coming intoventuri section 174. At or near reduced section 178, a portion of thewater vapor in the air may come out of saturation, such that waterdroplets are formed in the air. The water droplets may be borne in theair in a two-phase mixture of air and mist.

Air from return duct 110 may be introduced into mixing region 202through vent 206. In mixing region 202, a two-phase mixture of air andmist may mix with air from return duct 110. Air introduced from returnduct 110 may have been heated by components in data center 102. Heatfrom air from return duct 110 may cause a portion of the water dropletsin the two-phase mixture to return to saturation. In this manner, returnair may be cooled prior to being recycled to data center 102.

In some embodiments, a desiccant system removes water from source airbefore the air is used for cooling components in a building. In certainembodiments, air that has been dehumidified by a desiccant system iscooled using a direct evaporative cooler before being used to cool thecomponents.

In some embodiments, a desiccant system is used to remove water from atwo-phase mixture of air and mist. FIG. 3 illustrates one embodiment ofa data center including a venturi section and a desiccant wheel systemthat can be operated to dry out a two-phase mixture of air and waterdroplets. Cooling system 220 includes dehumidification system 222.Dehumidification system 222 includes venturi section 170, desiccantwheel system 224, and bypass 226.

Desiccant wheel system 224 includes desiccant wheel 228 and wheel driveunit 230. Desiccant drive unit 230 may rotate desiccant wheel 228 suchthat one portion of the desiccant wheel 228 is in the flow of supply airto heat producing components in data center 102, and another portion ofdesiccant wheel 228 is in the flow of return air from heat producingcomponents in data center 102.

Desiccant wheel 224 includes a desiccant material that removes waterfrom air as the air is drawn through desiccant wheel 228 by supply fan138. Air flowing through return duct 110 may be moved through a portionof desiccant wheel 228 to reactivate the desiccant material in thewheel. In some embodiments, heater 232 is operated to heat air in returnduct 110 before the air passes through the portion of desiccant wheel228 being reactivated. Heater 232 may be, in various embodiments, a gasheater or an electrical heater.

In some embodiments, air for reactivation of a desiccant device is drawnfrom outside air. For example, in the embodiment shown in FIG. 3, to useoutside air to reactivate desiccant wheel 228, return air damper 235 andreturn air bypass damper 152 may be closed or partially closed. Outsideair reactivation damper 236 may be opened to allow air moving device 144to move air through the portion of desiccant wheel 228 to bereactivated. In some embodiments, reactivation air is a mixture ofoutside air and return air. For example, both outside air reactivationdamper 236 and return air damper 235 may be partially open such that amixture of air from the computing room and outside is supplied to thereactivation portion of desiccant wheel 228.

FIG. 4 illustrates one embodiment of a desiccant wheel. Desiccant wheel240 includes desiccant material 242. Desiccant wheel 240 may be rotated(for example, using a belt drive) such that each portion of desiccantwheel 240 alternately passes through drying zone 244 and reactivationzone 246. A system of ducts (ducts are not shown in FIG. 4 for clarity)may be used to direct the stream of air to be dehumidified into dryingzone 244 and to direct a stream of air to reactivate (for example, dryout the desiccant material) into reactivation zone 246. Examples ofdesiccant material that may be used in a desiccant wheel include silicagel, activated carbon, calcium chloride, or lithium chloride. Asdesiccant wheel 240 is rotated, each portion of desiccant wheel 240cycles between a desiccation mode and a reactivation mode.

In some embodiments, a system for removing heat from electrical systemsincludes one or more desiccant dehumidification devices and anevaporative cooling device. Air flow to the dehumidification devices iscontrolled using an air flow control device.

In some embodiments, a data center includes electrical devices and acooling system. The cooling system includes a desiccant wheel and anevaporative cooling device downstream from the desiccant wheel. An airflow control device (for example, a set of louvers) is used to controlair flow to the desiccant wheel.

In some embodiments, air enters the unit through a set of louvers. Thelouvers are motorized to control inlet airflow. From there, the airpasses through a desiccant wheel. The desiccant wheel reduces themoisture content (or relative humidity %) of the air. The air passesthrough the fan compartment and then through an evaporative coolingmedia, which cools the air. Finally, the air is delivered to theconditioned space.

FIG. 5 illustrates one embodiment of data center with a desiccant wheelwith dampers to control air flow to the desiccant wheel, and a desiccantbypass duct. Cooling system 260. Cooling system 260 includesdehumidification system 262. Dehumidification system 262 includesdesiccant wheel system 234, bypass 264, wheel damper 266, and bypassdamper. Wheel damper 266 and bypass damper 268 may be connected tocontrol unit 150. Air flow to desiccant wheel 224 may be controlledusing wheel damper 266 and bypass damper 268. For example, whendehumidification is desired prior to air being introduced intoevaporative cooler 136, wheel damper 266 may be opened and bypass damper268 may be closed. If dehumidification is not desired, then wheel damper266 may be closed and bypass damper 268 may be opened. In someembodiments, the air supplied to evaporative cooler 136 is a mixture ofoutside air and air that has been dehumidified using one or more ofdesiccant wheel systems 262.

In some embodiments, multiple desiccant wheels are used to stage theamount of treated air to the space. Using ducted fresh air and dampermechanisms, the amount of air being treated may be increased ordecreased while maintaining a constant volume of air delivered to theconditioned space.

FIG. 6 illustrates one embodiment of data center with multiple desiccantwheels with dampers to control air flow to the desiccant wheels. Coolingsystem 280 includes desiccant wheel systems 282, desiccant duct system284, reactivation duct system 286, desiccant system bypass 287, andreactivation system bypass 288. Desiccant system main damper 289 anddesiccant system bypass damper 290 may be operated to control the sourceof air to supply fan 138. Reactivation main damper 291 and reactivationbypass damper 292 may be operated to control the flow of air toreactivate desiccant in desiccant wheel systems 282.

Each of desiccant wheel systems 282 includes desiccant wheel system 294,desiccant damper 296, and reactivation damper 298. Desiccant wheelsystem 294, desiccant damper 296, and reactivation damper 298 may becontrolled by control unit 150.

In some embodiments, one or more of desiccant wheel systems 282 areoperated to dehumidify air before the air is pass across evaporativecooler 136. The number of desiccant wheel systems that are active, andthe operating parameters of each active of desiccant wheel systems, maybe based on conditions in the data center or environmental conditions inor outside of the data center. The number of desiccant wheel systemsbeing reactivated may similarly be based on conditions in the datacenter or environmental conditions in or outside of the data center. Forexample, if the humidity of outside air is relatively low, all three ofdesiccant wheel systems 282, may be bypassed using desiccant systembypass 287. If, by contrast, the humidity of outside air is relativelyhigh, all three of desiccant wheel systems 282 may be operated byopening desiccant system dampers 296 and desiccant system main damper289. In some embodiments, only a sub-set of desiccant wheel systems 282are operated (for example, only 1 or 2 of desiccant wheel systems 282).In some embodiments, the air supplied to evaporative cooler 136 is amixture of outside air and air that has been dehumidified using one ormore of desiccant wheel systems 282.

FIG. 7 illustrates a data center with a heat exchanger for transferringheat from electrical loads in the data center to a desiccantreactivation loop. Cooling system 320 includes dehumidification system322, computing room exhaust duct 324, computing room exhaust fan 326,and reactivation loop 328. Reactivation loop 328 includes reactivationheat exchanger 330. Reactivation heat exchanger 330 may transfer heatfrom air passing through computing room exhaust duct 324 to air inreactivation loop 330. The heated air may be forced through thereactivation zone of desiccant wheel 228 to reactivate desiccant in thewheel. In one embodiment, reactivation heat exchanger 330 is a thermalwheel. In another embodiment, reactivation heat exchanger 330 is a plateand frame heat exchanger. In certain embodiments, air in computing roomexhaust duct 324 is pre-heated using heater 232 before passing throughreactivation heat exchanger 330.

In the embodiment shown in FIG. 7, air for the reactivation loop isdrawn from the main supply air duct to the computing room. In certainembodiments, however, air for the reactivation loop may be drawn fromoutside air instead of, or in addition to, a supply air duct.

FIG. 8 illustrates a data center with a solar heating system to promotedesiccant reactivation. Cooling system 360 includes dehumidificationsystem 362 and solar heating device 364. Solar heating device 364 maytransfer solar heat to air in reactivation loop 366. The heated air maybe forced through the reactivation zone of desiccant wheel 228 toreactivate desiccant in the wheel. In certain embodiments, solar heatingof air in reactivation loop 366 is supplemented using another heatsource, such as an electric heater or a gas heater.

In some embodiments, air for reactivation of a desiccant wheel fromprocess air that is being dehumidified using the desiccant wheel. In oneembodiment, air for reactivation of a desiccant wheel for a computingroom isolating from air passing through electrical systems in the datacenter.

In some embodiments, air for reactivating a desiccant wheel isintroduced on the same side of the wheel that air to be dehumidified.FIG. 9 illustrates one embodiment of a building with a desiccant wheelwith a counter-flow arrangement for desiccant reactivation. System 380includes reactivation duct system 382. The portion of desiccant wheel228 to be reactivated passes through reactivation duct system 382.Reactivation air moving device 384 moves air through portion ofdesiccant wheel 228 that is being reactivated (from right to left inFIG. 9). Reactivation duct system 382 is isolated return duct 110.

In some embodiments, a method of removing heat from electrical systemsin a building includes moving air stream through constricted section ofa duct to convert some of the water in the air into water droplets.

FIG. 10 illustrates one embodiment of cooling electrical systems in adata center using a two-phase mixture of air and water droplets. At 400,air is moved through a constricted section of a duct such that at leasta portion of water in the air is converted from water vapor to waterdroplets. In one embodiment, the constricted section is included in aventuri section of the duct. The water vapor may come out of saturationin a region of high velocity and low pressure.

At 402, a two-phase mixture including air and the water droplets ischanneled through a duct. In some embodiments, the two-phase mixtureincludes a mist. The two-phase mixture may be drawn out of a constrictedsection by an air moving device downstream from the constricted section.

At 404, electrical devices are cooled using the two-phase mixture. Insome embodiments, water is removed from the two-phase mixture by a waterremoval device such as an impingement plate system or a desiccant wheel.The drier air downstream from the water removal device may be passedacross an evaporative cooler. Air from the evaporative cooler may beused to cool electrical devices, such as servers in a data center.

In some embodiments, air flow or other operating characteristics in adehumidification system are controlled based on information from sensorsin or outside of a building. Types of sensors that may be used tocontrol dehumidification include temperature sensors, humidity sensors,pressure sensors, and air velocity sensors.

In some embodiments, a method for removing heat from electrical systemsincludes controlling a flow rate of a stream of air. The stream is movedacross a desiccant to remove dehumidify the air. The dehumidified air ismoved through a wetted media. Heat is removed from electrical systemsusing air from the wetted media.

FIG. 11 illustrates one embodiment of cooling electrical systems in adata center with controlled flow of air to a desiccant wheel. At 420, arate of air flow is controlled in a stream of air.

At 422, one or more of the streams of air is moved across a desiccant toremove water vapor from the air. In some embodiments, the air is passedthrough a desiccant wheel. In some embodiments, streams of air to two ormore desiccant wheels are independently controlled. Air flow to eachdesiccant wheel may be controlled based on conditions in the datacenter, outside air, or both. For example, if the source air beingintroduced into a cooling system is relatively dry, then dampers to oneor no desiccant wheels may be opened. If the source air to the coolingsystem is relatively humid, dampers may be opened to feed air to two ormore desiccant wheels.

At 424, the stream of air is passed across or through a wetted media. Insome embodiments, the air is passed through an evaporative cooler.

At 426, heat is removed from electrical systems using the air from thewetted media. In some embodiments, the electrical systems arerack-mounted computing devices in a computing room of a data center.

FIG. 12 is a fluid schematic diagram illustrating one embodiment of anevaporative cooling system including upper and lower evaporative mediabanks Evaporative cooling system 500 includes evaporative media upperbank 502 and evaporative media lower bank 504. In one embodiment, theevaporative media is Celdek media manufactured by Munters Corporation.Supply from a domestic water supply is provided through supply valve506. Water is fed to each of evaporative media upper bank 502 andevaporative media lower bank 504 through distribution manifolds 508.Water may also be supplied to distribution manifolds 508 from bottomsump 512 using pumps 510. Balancing valves 514 may be controlled tobalance flow to manifolds 508 and/or water levels in the media. Watermay be recirculated to sump 512 using three-way valves 520. Water may beexpelled or removed from the system through drain valve 522.

In certain embodiments, an evaporative cooling system may be operatedusing only one of the evaporative media banks while the flow through theother evaporative media banks is inhibited. Air from the evaporativecooler may be channeled through supply vent 402 to one or more rooms ofa data center.

Return air from the data center may be received in a return air chamber.In some embodiments, air in the return air chamber may be exhausted tothe outside through exhaust vents. In other embodiments, mixing airdampers may be operated to allow some or all of the return air to mixwith incoming outside air in a mixing region. In certain embodiments,air in a return air chamber is forced through a return air bypass. Flowthrough a return air bypass may be controlled by return air bypassdampers.

In certain embodiments, a cooling system includes a mechanical coolingsystem in addition, or instead of, an evaporative cooling system. In oneembodiment, a heat removal sub-system includes an air-conditioningrefrigerant sub-system. In another embodiment, a heat removal sub-systemincludes a cooling tower sub-system. In still another embodiment, a heatremoval sub-system includes a service water sub-system. In certainembodiments, a mechanical cooling system such as an air-conditioningrefrigerant system may be in direct heat transfer communication withcooling air in air handling sub-systems, such as air-handling sub-system104 described above relative to FIG. 1.

In certain embodiments, operation of one or more of subsystems (e.g.,CRACs) may be controlled to increase or decrease the total output of thecooling system. In certain embodiments, the number of units switchedfrom normal to free cooling mode may be selected to achieve a desiredlevel of cooling performance. In some embodiments, switching betweenoutside air and return air and/or shut down of the chillers may beprogrammed to occur in stages.

In the figures described above, connections between the control unit anddampers and fans are not shown for clarity. In various embodiments,however, any or all of the dampers shown in the figures may beautomatically controlled (for example, a programmable logic controller.)In addition, any or all of the dampers illustrated in the figures mayinclude an actuator or other mechanism for controlling the position of adamper.

Although in many of the embodiments described herein, non-mechanicalcooling with dehumidification is described for illustrative purposes forelectrical systems in a data center, dehumidification may, in variousembodiments, be performed for other types of buildings and other typesof heat producing components. For example, non-mechanical cooling withdehumidification may be used to cool a power plant, a manufacturingplant, a medical care facility, or an office building.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A data center, comprising: a plurality ofelectrical devices comprising heat producing components; and a coolingsystem, comprising: one or more desiccant wheels; one or moreevaporative cooling devices downstream from at least one of thedesiccant wheels, wherein the one or more evaporative cooling devicesare configured to evaporate a liquid into a stream of air flowingthrough the one or more evaporative cooling devices to cool the streamof air; one or more air moving devices; and one or more air flow controldevices; wherein at least one of the air moving devices is configured tomove air through at least one of the desiccant wheels, at least of theone or more evaporative cooling devices, and at least one of the heatproducing components of the electrical devices, wherein the coolingsystem is configured such that at least a portion of the stream of airthat flows through the one or more evaporative cooling devices flowsthrough at least one of the desiccant wheels upstream of the one or moreevaporative cooling devices and at least another portion of the streamof air that flows through the one or more evaporative cooling devicesbypasses the at least one of the desiccant wheels upstream of the one ormore evaporative cooling devices; wherein at least one of the air flowcontrol devices is configured to adjust the at least a portion of thestream of air that flows through the at least one of the desiccantwheels.
 2. The system of claim 1, wherein the cooling system isconfigured to move air through at least one of the one or more desiccantwheels to reactivate the desiccant wheel, wherein the cooling system isconfigured to transfer heat from the electrical devices to at least aportion of the air being supplied to the at least one desiccant wheel topromote reactivation of the at least one desiccant wheel.
 3. The systemof claim 1, wherein the one or more desiccant wheels comprise two ormore desiccant wheels, wherein each of at least two of the desiccantwheels is configured to dehumidify a different stream of air.
 4. Asystem for removing heat from electrical systems, comprising: one ormore dehumidification devices comprising a desiccant; one or moreevaporative cooling devices configured to evaporate a liquid into astream of air flowing through the one or more evaporative coolingdevices to cool the stream of air; one or more air moving devices; andone or more air flow control devices; wherein at least one of the airmoving devices is configured to move air through at least one of thedehumidification devices, at least of the one or more evaporativecooling devices, and one or more of the electrical systems, wherein thesystem is configured such that at least a portion of the stream of airthat flows through the one or more evaporative cooling devices flowsthrough at least one of the one or more dehumidification devicesupstream of the one or more evaporative coolers and at least anotherportion of the stream of air that flows through the one or moreevaporative cooling devices bypasses the at least one dehumidificationdevice; and wherein at least one of the air flow control devices isconfigured to adjust the at least a portion of the stream of flow airthat flows through the at least one of the dehumidification devices. 5.The system of claim 4, wherein at least one of the dehumidificationdevices comprises a desiccant wheel.
 6. The system of claim 4, whereinthe at least one airflow control device comprises one or more sets ofdampers, wherein the at least one airflow control device is configuredto open and close at least one of the dampers to change a rate of airflow through the at least one dehumidification device.
 7. The system ofclaim 4, further comprising one or more ducts configurable to bypass atleast one of the dehumidification devices.
 8. The system of claim 7,wherein the at least one air flow control device comprises a controller,wherein the controller is configured to control a rate of flow of airthrough the at least one of the dehumidification devices.
 9. The systemof claim 8, further comprising one or more temperature sensors coupledto the control system, wherein the control system is configured tocontrol an air stream in the one or more ducts based at least in part oninformation from at least one of the temperature sensors.
 10. The systemof claim 8, further comprising one or more humidity sensors coupled tothe control system, wherein the control system is configured to controlan air stream in the one or more ducts based at least in part oninformation from at least one of the humidity sensors.
 11. The system ofclaim 4, further comprising a mixing plenum, wherein the system isconfigured to mix outside air with air modified by at least one of thedehumidification devices.
 12. The system of claim 4, wherein the one ormore dehumidification devices comprises two or more desiccant wheels,wherein each of at least two of the desiccant wheels is configured todehumidify air in a different stream of air.
 13. The system of claim 12,wherein the one or more air flow control devices comprise two or moreair flow control devices, wherein each of at least two of the air flowcontrol devices is configurable to control a rate of air flow through adifferent one of the desiccant wheels.
 14. The system of claim 4,further comprising a constricted section in a duct upstream from atleast one of the dehumidification devices, wherein at least one of theair moving devices is configured to move air through the constrictedsection of the duct such that at least some water in the air isconverted from water vapor to water droplets.
 15. The system of claim 4,wherein the electrical devices are in a data center, wherein the systemis configured to move heated air from the electrical devices in the datacenter through at least one of the desiccant wheels, wherein the heatedair promotes reactivation of the desiccant wheel.
 16. The system ofclaim 4, further comprising a solar heating device configured to heatair, wherein the system is configured to move at least a portion of theair heated by the solar heating device through at least one of thedesiccant wheels to promote reactivation of the desiccant wheel.
 17. Thesystem of claim 4, further comprising a heat exchanger configured totransfer heat from a first stream of air heated by the electricalsystems to a second stream of air, wherein the system is configured tomove at least a portion of the air from the second stream of air throughat least one of the desiccant wheels to reactivate the desiccant wheel.18. The system of claim 4, further comprising one or more venturisections in at least one of the ducts, wherein the venturi section isconfigured to reduce pressure in at least a portion of the air beingused to reactivate at least one of the desiccant wheels.
 19. A method ofremoving heat from electrical systems, comprising: controlling a rate ofa flow of one or more streams of air; moving at least a portion of atleast one of the streams of air across a desiccant to remove water vaporfrom the air; combining the portion of the at least one stream of airthat moves across the desiccant with another portion of the at least onestream of air that bypasses the desiccant; moving at least a portion ofthe combined stream of air through a wetted media; and removing heatfrom one or more electrical systems using at least a portion of the airfrom the wetted media.
 20. The method of claim 19, further comprisingmoving at least a portion of air heated by the electrical systems acrossat least a portion of the desiccant to reactivate the desiccant.
 21. Themethod of claim 19, further comprising: solar heating a stream of air;and moving at least a portion of the solar heated air across thedesiccant to reactivate the desiccant.
 22. The method of claim 19,wherein controlling a rate of a flow of one or more streams of aircomprises operating one or more dampers to change a rate of air flow tothe desiccant.
 23. The method of claim 19, wherein controlling a rate ofa flow of one or more streams of air comprises controlling a rate of aflow of a first stream of air to a first desiccant wheel and controllinga rate of a flow of a second stream of air to a second desiccant wheel,wherein moving at least a portion of the at least one of the streams ofair across a desiccant comprises passing the first stream of air throughthe first desiccant wheel and passing the second stream of air throughthe second desiccant wheel.